LM96063CISDXSLASHNOPB datasheet(9/46 Pages) TI2

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LM96063

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SNIS149B – NOVEMBER 2011 – REVISED MARCH 2013

FUNCTIONAL DESCRIPTION

The LM96063 Remote Diode Temperature Sensor with Integrated Fan Control incorporates a

ΔVBE-based

temperature sensor utilizing a Local or Remote diode and a 10-bit plus sign

ΔΣ ADC (Delta-Sigma Analog-to-

Digital Converter). The pulse-width modulated (PWM) open-drain output, with a pull-up resistor, is driven by a 12-

point temperature to duty cycle look-up table (LUT) and can directly drive a PWM input of a 4-pin fan in order to

modulate it's speed enabling optimum system acoustic performance. The LM96063 LUT fan control algorithm

also includes a smoothing function that allows the PWM duty cycle to gradually change over a programmed time

interval when switching from one level to the next in the LUT. When running at a frequency of 22.5kHz the PWM

output resolution is 0.39%. The LM96063 includes a TACH input that can measure the speed of a fan using the

pulses from a 3 or 4 pin fan’s tachometer output. The LM96063 includes a smart-tach measurement mode to

accommodate the corrupted tachometer pulses when using switching transistor power drive to modulate the fan

speed. The LM96063 has an ALERT open-drain output that will be pulled low when the measured temperature

exceeds certain programmed limits when enabled. Details are contained in the sections below.

The LM96063 can measure a diode-connected transistor such as the MMBT3904 or the thermal diode found in

an FPGA, ASIC, Processor or any other device built on an SOI process accurately. The LM96163 is identical to

the LM96063 except the TruTherm BJT Beta compensation is included. Thermal diode TruTherm BJT

compensation circuitry is required when sensing thermal diodes mainly found in 22/45/65/90 nm conventional

bulk CMOS non SOI processes.

The LM96063's two-wire interface is compatible with the SMBus Specification 2.0. For more information the

reader is directed to www.smbus.org.

In the LM96063 digital comparators are used to compare the measured Local Temperature (LT) to the Local

High Setpoint user-programmable temperature limit register. The measured Remote Temperature (RT) is digitally

compared to the Remote High Setpoint (RHS), the Remote Low Setpoint (RLS), and the Remote T_CRIT

Setpoint (RCS) user-programmable temperature limits. An ALERT output will occur when the measured

temperature is: (1) higher than either the High Setpoint or the T_CRIT Setpoint, or (2) lower than the Low

Setpoint. The ALERT Mask register allows the user to prevent the generation of these ALERT outputs. A TCRIT

output will occur when the measured temperature is higher than the T_CRIT Setpoint.

The TCRIT function and the look-up table temperature hysteresis can be set separately. The hysteresis value

associated with the TCRIT output is set in the Remote T_CRIT Hysteresis Register. The value associated with

the look-up table function is set in the Lookup Table Hysteresis Register.

The LM96063 may be placed in a low power Standby mode by setting the Standby bit found in the Configuration

allow the PWM output signal to continue, or not, by programming the PWM Disable in Standby bit in the

Configuration Register.

The Local Temperature reading and setpoint data registers are 8-bits wide. The format of the 11-bit remote

temperature data is a 16-bit left justified word. Two 8-bit registers, high and low bytes, are provided for each

setpoint as well as the temperature reading. A digital filter may be invoked for remote temperature readings that

increases the resolution from 11-bits to 13-bits. The temperature readings are also available in an unsigned

format allowing resolution above 127°C. Two Remote Temperature Offset (RTO) Registers: High Byte and Low

Byte (RTOHB and RTOLB) may be used to correct the temperature readings by adding or subtracting a fixed

value based on a different non-ideality factor and series resistance of the thermal diode if different from the

thermal diode found in the Intel processors on 45 nm process. See section DIODE NON-IDEALITY.

ALERT and TCRIT OUTPUTS

In this section we will address the ALERT and TCRIT active-low open-drain output functions. When the ALERT

Mask bit in the Configuration register is written as zero the ALERT interrupts are enabled.

The LM96063's ALERT pin is versatile and can produce three different methods of use to best serve the system

designer: (1) as a temperature comparator (2) as a temperature-based interrupt flag, and (3) as part of an

SMBus ALERT System. The three methods of use are further described below. The ALERT and interrupt

methods are different only in how the user interacts with the LM96063.

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